The present invention relates generally to valve units. More specifically, the present invention relates to a valve unit including a flexable nozzle and a valve.
In the manufacture of certain types of non-returnable packages for dairy products the packing containers are filled with the help of metering pumps. Such pumps are usually in the form of piston pumps which at each pumping stroke mete out the desired amount of liquid to a chamber connected to the pump, from where the liquid is transferred to the packing container which is to be filled. In order to prevent afterdripping from the outlet end of the chamber when highly viscous liquids, e.g. yogurt or the like, are pumped, the outlet opening is usually provided at the orifice with a wire screen through which the liquid is pressed by the pump. The wire screen retains the liquid column present in the chamber, not pumped out during the pumping stroke, since owing to the surface tension of the liquid, the same cannot leak out without the active co-operation of the pump. This principle, in general, is working well, but cannot be used, of course, for non-homogeneous liquids, e.g. yogurt with pieces of fruit, nuts or the like. No practical solution of the afterdripping problem with this type of liquids filling has been suggested up to now.
It is one main object of the present invention to provide a valve unit which is particularly suitable to be used in association with non-homogeneous liquids, e.g. fruit yogurt or the like and which is not subject to the disadvantages of the valve units known up to now.
It is a further main object of the present invention to provide a valve unit which is designed so that its function is not hindered by liquids which contain relatively large solid or semi-solid particles.
It is a yet further object of the present invention to provide a valve unit which is easy to clean and which meets the high demands of hygiene.
These and other objects have been achieved in accordance with the invention in that a valve unit including a nozzle and a valve has been given the characteristic that the nozzle is made of a flexible material and is provided with a slit which in the absence of external forces acting upon the nozzle is kept shut through the flexibility of the nozzle. By placing several slits in such a manner that between them they form lugs capable of being folded out, the liquid can pass the nozzle without appreciable resistance on being subjected to the action of the pump. When the pumping stroke has stopped, the flexibility of the nozzle material and the pressure difference between the inside and the outside of the nozzle have the effect that the lugs are folded back again so that the slit-shaped openings are closed. This means that the nozzle is shut so that the liquid column present in the chamber is retained and the risk of afterdripping is eliminated. Since the nozzle does not contain any net or other parts of limited area through which the liquid has to pass, the nozzle is particularly suitable for thick, non-homogeneous products. Furthermore, a nozzle of advantageous fluidic design is obtained which permits a high flow rate and therefore has a high capacity.
In order to reduce further the flow resistance of the nozzle, the nozzle part may be given the form of a compressed tube and be made of a thinner and particularly flexible material. As a result the force which is required to widen the nozzle maximally when the liquid is to pass will be very small, but at the same time there is a greater risk that the nozzle will not shut sufficiently tightly to prevent afterdripping. In accordance with a preferred embodiment of the invention, a flexible nozzle part may be combined with a device adapted so as to change the volume in the chamber at the outlet orifice of which the nozzle is situated. After each pumping stroke the volume of the chamber is reduced, so that a vacuum is created which ensures a rapid and complete closure of the openings of the flexible nozzle. This embodiment of the valve unit in accordance with the invention is particularly suitable for high-capacity filling machines.
Further embodiments of the arrangement in accordance with the invention have been given, moreover, the characteristics which are evident from the description below.